Sun, Alcatel back spec for multilevel signaling backplanes

SAN JOSE, Calif. " A group of seven semiconductor and systems companies unveiled an alliance and draft specification Wednesday (Nov 26) for high-speed multilevel signaling, potentially gaining an edge over a group advocating a rival binary technology.

The Multi-Level Signaling Alliance was formed quietly in July to promote PAM4 signaling for serializer/deserializers used in backplane systems. It expects to present to formal standards organizations its spec in the first quarter of next year. That's at least three months ahead of the timeline of a rival group led by Xilinx Inc. backing binary technology.

The MLS Alliance is chaired by Bill Hoppin, vice president of marketing and strategic sales for interconnect startup Accelerant Networks (Beaverton, Ore.). Other major members include Accelerant's ASIC partner Agere Systems, Ethernet switch startup Force10 and OEMs Alcatel and Sun Microsystems. Rambus is not listed as a member though the company designs PAM-4-based serdes.

The new alliance was formed as vendors have been battling behind the scenes over the use of binary or PAM4 technology in high-speed backplanes and edging to define standards for the technology at the 10Gbit/second level.

In early October, Xilinx Inc. and four partners unveiled ad hoc efforts to develop a physical layer standard for a 10 Gbit/s serdes based on binary technology. The so-called Unified 10Gbit Physical-Layer Initiative (UXPi) includes Applied Micro Circuits Corp., IBM Microelectronics, Infineon and Texas Instruments. UXPi is currently trying to recruit OEM members to review their draft spec which they hope to submit to formal standards groups by June.

The UXPi effort is seen as an outgrowth of work in the Optical Internetworking Forum to set 10Gbit/s backplane standards. Both alliances hope to influence the evolution of interconnects such as PCI Express and RapidIO as they move from 2.5 to 10 Gbit/s data rates.

Binary technology, used widely today, is generally seen as the least complex of the two approaches, but harder to extend to 10Gbit/s data rates and beyond than PAM4.

A representative of the MLS Alliance was not immediately available for comment.